Out of Plumb

A plumb bob, or plummet, is a weight, usually with a pointed tip on the bottom, suspended from a string and used as a vertical reference line, or plumb-line. It is essentially the vertical equivalent of a "water level"

Below are some pictures where a building is not vertical nor perpendicular.

Wikipedia Entry for Plum-bob

Out of Plumb Picture    Out of Plumb 2 Picture